function displayImage(index, parent){
    var images = document.getElementById(parent).getElementsByTagName("div");
    for(var i = 0; i < images.length; i++) {
        var image = images[i];
        if (image.className != 'pimage')  { continue }
        if(i == index-1) {
            image.style.display="block";
        } else {
            image.style.display="none";
        }
    }
}